CG Cookie

CG Cookie teaches how to use Blender 3d, Unity, and sculpting. I recommend starting with their 2d basic art concept courses. They have the individual courses available, but they've organized the course into "learning flows" that track your progress.  The community checks your homework and keeps you inspired. They have several good introductory videos available for free, but I recommend purchasing an annual subscription to get the full courses. You can also purchase a monthly subscription. They are the best online art courses I've found available and they have great instructors who make things easy to follow and understand.